Paper 
Title 
Page 
WEAY04 
Analysis of the magnetized friction force

210 

 A. V. Fedotov
BNL, Upton, Long Island, New York
 D. L. Bruhwiler
TechX, Boulder, Colorado
 A. O. Sidorin
JINR, Dubna, Moscow Region



A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, we present our insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.


WEBY05 
Simulating dynamical friction in wigglerbased highenergy electron coolers, including finitetime effects

0 

 G. I. Bell, D. T. Abell, D. L. Bruhwiler, R. Busby, P. Messmer
TechX, Boulder, Colorado
 I. BenZvi, A. V. Fedotov, V. Litvinenko
BNL, Upton, Long Island, New York
 A. O. Sidorin
JINR, Dubna, Moscow Region



The proposed RHICII luminosity upgrade includes a novel electron cooling section, using ~55 MeV electrons to cool fullyionized gold. We present simulations of the dynamical friction force exerted on the Au ions. Rather than a strong solenoid, a long helical wiggler magnet is used to provide focusing and suppress recombination. In the rest frame of the relativistic electron and ion beams, with nonrelativistic motion and electrostatic fields, the Lorentz transformed wiggler field yields strong, rapidlyvarying electric fields. The VORPAL simulation framework applies a semianalytic binary collision algorithm, in which ionelectron collisions are modeled pairwise. This model is combined with standard particleincell (PIC) techniques, through an operatorsplitting approach, to include the effects of external fields. Charge shielding due to electronelectron interactions is also included via PIC. Simulated friction results are compared with BETACOOL, which integrates the standard unmagnetized formulas. With finite interaction times and electron wiggle motion correctly included, we find good agreement with VORPAL.

